Adhesive



Patented June 13, I939 ADHESIVE.

Lewis Davis, Worcester, Mass,

assignor to -McLaurin-Jones 00., Brookfield, -:Mass., ;a corporation ofMassachusetts 7 No Drawing. Application December;3, 1936,

.Serial No. 114,038

3 Claims.

This invention relates to a Water soluble adhesive for the preparationof gummed papers and other cellulosic sheet materials used in themanufacture of labels, stamps, and the like.

The surface characteristics of many articles are such that it isdifficult to make a label or stamp adhere'to them. Important examples ofsuch articles are aluminum ware, various other metal articles made bystamping or drawing operations or which have plated surfaces,grapefruit, oranges, lacquered and enamel surfaces, and articles made ofBakelite, and other plastics. The present invention aims to solve theproblem presented by these conditions.

In many cases the surface characteristics which prevent adhesion of thelabel thereto is due to the presence of an extremely thin film of oilyor Waxy material. This is not true in other cases, however, which givepractically as much trouble, and the real cause of the difficulty inproducing a satisfactory bond between the label and such a surfaceappears to defy analysis. I have found, however, that these difficultiescan be effectually overcome by coating the paper or other cellulosicmaterial which forms the main body of the label stock with a noveladhesive of the following composition:

Parts Hydroresin 25 Rezinel 7,5 Animal glue 12.5 Potassium hydroxide .5Water a 85 In this formula the chief adhesive agent is the glue. Itshould be some good grade of a glue of animal origin such as bone, hide,fish or animal glue, or mixtures of the same, all such glues beinghereafter included in the term animal glue. Another essentialconstituent is the hydroresin, this being the common commercial name fortrihydroxylethylamine abietate. It is of a resinous or pitchy nature andhas the property of blending with the glue and maintaining itindefinitely in a sticky and tacky condition. In some measure thisundoubtedly is due to its ability to hold water and to refuse to give itup except under unusual conditions, acting in this respect like a stickypitch. While other substances of this general nature are available, theyall have characteristics or limitations which are objectionable for thepurposes of this invention. A diligent search has failed to disclose anycompletely satisfactory substitute for hydroresin. The rezinel is acommon commercial product con- (Cl. 134-23.?) I

sisting of a mixture .of ,p olyn' erized terpenes.

Itcomes ,in, different; grade.-. andthe No. .2 grade is preferred forthe present purposes. ,It ,serves inthe mixtureabove describedas-asmoothing or plasticizing ,agent for: the ,hydroresin ,and the 5 glueandit is especially:valuableinthe machine application of the adhesive tothe sheet-material. The potassium hydroxide, or equivalent causticalkali, appears to perform the dual function of cutting or saponifyingany oily, greasy, or waxy film on the surface to which the label isapplied, and to etch said surface to a minute degree, both of theseresults enabling the glue to obtain a stronger hold on the surface. Thisconstituent is not absolutely necessary for many purposes, but

it preferably is used because it practically always produces a strongerbond between the label and the article to which it is secured, and inapplying labels to surfaces which are at all oily,

greasy or waxy it performs a very important function in improving thestrength of the bond. The proportion of water used in the mixturenecessarily will depend, to a large degree, upon the consistencydesired.

In making up the adhesive above described it is preferable first todissolve the caustic alkali in about twenty-five parts of water heatedto the boiling point, or thereabouts. The hydroresin and the rezinelthen are added, these ingredients preferably having first been heated toa temperature of, say, 50 C. prior to stirring them into the alkalisolution. The glue, which desirably is in a granulated form, is firstdissolved in the remaining proportion of the water, say sixty parts,heated to a temperature of 80 C., or thereabouts, and the two solutionsthen are mixed together and stirred until they are well blended.

While the formula above given is. preferred, it

will be understood that other constituents can be added and sometimesare of value. For example,

other plasticizing agents, such as urea, are sometimes useful. Whenslower drying is necessary, such agents as methyl abietate, rosin oil,or carbitol can be added in suitable proportions to give the desiredresults. Carbitol is a commercial fixed. At the same time it should beunderstood still producing good results. A satisfactory range ofproportions of the constituents is as follows:

Water, varying with the consistency desired, but

usually from to parts.

The adhesive usually is applied to the paper or other sheet materialwhile the latter is in the form of a web, the application being made inany suitable form of gumming machine. From the machine the paper istaken through a dryer where the coating is thoroughly dried, after whichthe product is ready for shipment to the printer or other user. While,as above stated, the mixture retains its adhesiveness indefinitely afterthe labels have been moistened and applied to the work, nevertheless thecoating dries hard and remains in a hard and substantially non-tackycondition during printing or other label manufacturing operations andthe stock does not cake in the rolls or stacks. Consequently, it doesnot require interleaving.

Having thus described my invention, what I desire to claim as new is:

1. A water soluble adhesive composition comprising a mixture of animalglue, "Hydroresin and Rezinel, the Hydroresin being the predominatingconstituent, and the proportion of glue being less than that of theHydroresin, the Rezinel being present in a substantial percentage.

2. A water soluble adhesive composition comprising a mixture of animalglue, Hydroresin and Rezinel, and caustic alkali, the Hydroresin beingthe predominating constituent, and the proportion of glue being lessthan that of the Hydroresin, the "RezineP being present in a substantialpercentage, and the proportion of caustic alkali being very small.

3. A water soluble adhesive composition con- 1 sisting essentially ofthe following constituents:

Parts Hydroresin 201 to 25 Animal glue 3 to 15 Rezinel 0 to 8 Potassiumhydroxide 0 to 1 LEWIS DAVIS.

